A computational thermodynamic model of the Mg-Al-Y system

Abstract

The ternary system Mg-Al-Y was thermodynamically modeled based on the optimization of the binary sub-systems Mg-Al, Mg-Y and Al-Y using the CALPHAD approach. Mg-Al data was taken from the COST507 database, whereas the other two binary subsystems were reoptemised in this work. Liquid phases were described by the Redlich-Kister polynomial model, whereas the intermediate solid solutions were described by the sublattice model. Ternary interaction parameters were introduced to enable the best representation of the experimental data while considering the occurrence of the ternary compound Al4MgY. The constructed database is used to calculate and predict thermodynamic properties, binary phase diagrams of Al-Y and Mg-Y, and liquidus projections of the ternary Mg-Al-Y. The phase diagrams and the thermodynamic properties calculated with the evaluated parameters were in good agreement with the corresponding experimental data from the literature. The predicted invariant points in the Mg-Al-Y system were 16 ternary four-phase-equilibria points; 7 ternary eutectic points, 8 ternary quasi peritectic points, and one ternary peritectic point. Further, 15 ternary three-phase-equilibria points were determined; 8 saddle points, and 7 binary eutectic points